Studies of Xenon Chlorides and Other Xenon Compounds by the Mössbauer Effect in 129Xe

The compounds XeCl₂ and XeCl₄ have been made in the beta decay of ICl₂⁻ and ICl₄⁻ containing radioactive ¹²⁹I. The electric quadrupole interaction in the 39.6‐keV excited state of the ^129Xe nucleus is employed to study these substances by the Mössbauer effect. The decay products are compared with XeF₂ and XeF₄ and with the parent ions. It is shown that the decays ICl₂⁻→XeCl₂ and ICl₄⁻→XeCl₄ both result in the recall of 0.2 electrons per bond from each ligand to the central atom. In the xenon halides the charges per fluorine are − 0.72 and per chlorine are − 0.5. The assumption of pure $p_{\sigma }$ bonding in the xenon halides is tested by the isomer shifts. With its aid the shifts can be calibrated by the quadrupole couplings. A shielding constant obtained from Hartree‐Fock calculations by Wilson is then used to relate p‐electron to s‐electron transfer, which is next employed to examine the charges on the xenon atom in XeO₄ and XeO₆⁻⁴. The former is prepared in beta decay, the latter equivalently either in beta decay or in bulk. It is shown that directed ${\mathrm{sp}}^3{d}^2$ hybrid bonds for XeO₆⁻⁴ are inconsistent with the measured isomer shift. The recoilless fractions and linewidths are tabulated for a number of xenon compounds.